Error while generating an array of pointer

Error while generating an array of pointer

Trying to implement below code for some assignment but getting an error
for malloc array generation "[Error] conflicting types for 'stack'" Any
Help ?? Thanks in Advance.
#include<stdio.h>
#include<stdlib.h>
struct treenode
{
char info;
struct treenode *firstchild;
struct treenode *next;
int flag;
};
typedef struct treenode *NODEPTR;
NODEPTR *stack;
// Trying to create array here
stack=(NODEPTR*)malloc(sizeof(NODEPTR)*20);
int main()
{
printf("YO\n");
return 0;
}